FGF21 ameliorates hepatic fibrosis by multiple mechanisms

Background Previous study reports that fibroblast growth factor 21 (FGF21) could ameliorate hepatic fibrosis, but its mechanisms have not been fully investigated. Methods and results In this study, three models were used to investigate the mechanism by which FGF21 alleviates liver fibrosis. Hepatic fibrosis animal models were respectively induced by CCL 4 and dimethylnitrosamine. Our results demonstrated that liver index and liver function were deteriorated in both models. Hematoxylin and eosin and Masson’s staining showed that the damaged tissue architectonics were observed in the mice of both models. Treatment with FGF21 significantly ameliorated these changes. ELISA analysis showed that the serum levels of IL-1β, IL-6 and TNF-α were significantly elevated in both models. However, administration of FGF21 significantly reduced these inflammatory cytokines. Real-time PCR and Western blot analysis showed that treatment with FGF21 significantly decreased mRNA and protein expressions of collagenI, α-SMA and TGF-β. Platelet-derived growth factor-BB (PDGF-BB) stimulant was used to establish the experimental cell model in hepatic stellate cells (HSCs). Real-time PCR and Western blot analysis demonstrated that the expression of collagenI and α-SMA were significantly upregulated by this stimulant in model group. Interestingly, our results showed that mRNA and protein expressions of leptin were also significantly induced in PDGF-BB treated HSCs. Administration of FGF21 significantly reduced leptin expression in a dose dependent manner and these effects were reversed in siRNA (against β-klotho) transfected HSCs. Furthermore, the leptin signaling pathways related protein p-ERK/t-ERK, p-STAT3/STAT3 and TGF-β were significantly downregulated by FGF21 treatment in a dose dependent manner. The expressions of SOCS3 and Nrf-2 were enhanced by treatment with FGF21. The underlying mechanism may be that FGF21 regulates leptin-STAT3 axis via Nrf-2 and SOCS3 pathway in activated HSCs. Conclusions FGF21 ameliorates hepatic fibrosis by multiple mechanisms.